Compound air-compressor.



PATENTED MAR. 1'7, 1903.

No. '723,001l

G. W. MARSH.

COMPOUND 'AIR COMPRESSOR.

APPLICATION FILED DEO. 30, 1901.

N0 MODEL.

UNITED STATES PATENT OEEICE.

GEORGE W. ll/IARSH, OF OAKLAND, CALIFORNIA.

CONI POUND AIR-COMPRESSOR?v SPECIFICATION forming part of Letters Patent No. 723,001, dated March 17, 1903. Application filed December 30, 1901. Serial No.v87.737. (No model.)

To all whom zit may concern.: Be it known that I, GEORGE W. MARSH, citizen of the United States, residing in Oakland, county of Alameda, State of California, have invented an Improvement in Compound Air-Compressors; and I hereby declare the following to be a full, clear, and exact description of the same.

My invention relates to improvements in air-compressors such as are designed for use particularly on locomotives. Its object is to afford a means of increasing the capacity'of the compressor by which the reservoirs su pplying the air-brakes are charged.

It consists, essentially, in the combination, with high-pressure motor and air cylinders arranged in line, pistons reciprocable there-VV in and movable in unison, and means for sup? plying fluid to said-motor-cylinder, of supplemental or low-pressure motor and air cylinders, pistons movable in unison in said'cylinders, connections between `the high-pressure and low-pressuremotor-cylinders where-A by the exhaust from the first is utilized as a motive power to drive the piston in the second, inlet-ports in each .of said air-cylinders,- and connections between said air-cylinders whereby the exhaust from the lowpressure air-cylinder is delivered into the high-pressu re air-cylinder and theamount of air in the latter increased by the amount of air thereby delivered, so that the act of compression by the piston of the cylinder so charged will deliver a proportionately greater quantity of air to the reservoir on eachreciprocation of said piston.

My invention also comprises details which will be more fully set forth hereinafter, having reference to the accompanying drawing, in which the figure is a vertical central section through the compressor.

A represents a motorcylinder,and B an air-compressor cylinder, arranged in line and operating after the manner usual in such apparatus. For the clear understanding of my invention I shall detail certain of these parts.

Pistons 2 and 3 are reciprocable in their' boxes 5. `A steam-chest 6 is disposed in suitable relation to the motor-cylinder A, and the feed and exhaust to and from the cylinderis controlled bya piston-valve 7. Live steam is admitted to the chest through the port 8. The operation of the valve 7 is eiected by means of a slide-valve mechanism 9 and a balance-valve 10, both of which being old and forming no part of my invention need not here be described at length, as theoperation is clearly understandable from the drawings. Inlet and exhaust ports 11and-12 deliver and discharge themotive fluid to and from cylinder A. Air is taken in and exhausted to and from the main compressor-cylinder B through ports 13 and 14 on alternate reciprocations of the piston 3. The ports 13 and 14 open into respective chambers 15 and 16, in which are the check-valves 17 and 18, the valves 17 serving to admit air from the outer atmosphere on suction and to close on compression, whereupon the valves 18 open and allow the compressed iiuid to ow through passage 19 to the air-reservoir. On suction the'valves 18 are closed.

In operation, assuming an initial steampressure of one hundred pounds acting ou the piston ofthe motor-cylinder A and a pressure f four or five atmospheres in the reservoir, the piston 3 will move nearly the length of thecylinder B before the air in the cylin- Y der is sufficiently compressed to overcome the tension on the valves 18 and allow the air to pass to the reservoir. The result is that the period of discharge from cylinder B is very brief. The piston is not, in fact, permitted to finish its stroke before reversal begins, and fullest effect of compression is not realized.

' My invention-resides in supplying the cylinder B with a charge of air in excess of that which it has drawn in through one or the other of the valves 17, so that the moment the piston 3 starts compression the cylinder B will contain air under pressure of two or more atmospheres, while ordinarily that pressure at the beginning of the stroke is represented by but one atmosphere. These results are achieved by the following means:

C isa low-pressure motor-cylinder suitably disposed in relationv to the' cylindervA and is designed to utilize the exhaust of the latter for its motive-power purposes.

D is an air-cylinder in which the piston 21 is movable. This piston is connected byv means of the rod 22` (slidable through the stuffing-boxes 23) with the piston 24 of the cylinder C. The motive duid, as steam, is exhausted through the ports 1l and 12 of the cylinder A, thence through either of the passages 25 and 26 to cylinder 6 to drive the piston 24 inone direction or the other. A piston-valve 27, movable in a valve-chamber 28, has its ends projecting into the passage-ways 25 and 26 and is adapted to be operated by the steam-pressure alternately exerted in said passages to uncover one or the other of the ports 29 29 and allowl exhaust from the cylinder C to take place out through the port 30. The cylinder D is provided with ports 3l and 32, opening into respective valve-chambers 33 and 34, in which are the check-valves 35 and 36, the valves 35 serving to admit air from the outer atmosphere on suction and the valves 36 to open on compression and allow discharge to take place into the passage-way or port 37, which enters the cylinder B intermediate of the ends of the latter.

In operation, assuming the motor-cylinders and the air-cylinders to be correspondingly uniform in size and the initial steam-pressure on the piston 2 to be one hundred pounds, the moment exhaust occurs, for example, through the port 11 (which will be when the pistons 2 and 3 are at the end of their stroke and the piston 3 has just drawn in a charge of air through one of the valves 17) and the piston 24 being at the end of the cylinder C corresponding to the passage 26 the pistonvalve 27 will be moved by reason of the pressure in the passage 26 to close the port 29. Consequently the exhaust iluid from cylinder A will act on piston 24 of cylinder C to cause it and the piston 2l to move rapidly toward the other end of their respective cylinders. As the pressure exerted on piston 24 is approximatelyone hundred pounds, less loss by expansion, &c.,lthe air in cylinder D is driven throng-h the ports 3l and 37 into the cylinder the relatively greater pressure on piston 24 the pistons 24 and 2l have completed their stroke before the piston 3 has crossed the port 37. Consequently when the piston 3 moves across the cylinder B it acts on twice the quantity of air that it would were the supply dependent entirely on valves 17.

The object of interposing the port 37 centrally of cylinder B, as shown, is to relieve the high-pressure and low-pressure motorcylinders of any excessive back pressure on their pistons, which might result in the stoppage of the apparatus in case the initial steampressure was insufticient to fully elect compression in the two compressor-cylinders, for, supposing the exhaust-pressure from cylinder A was only sufficient to move the pistons 2l and 24 part Way across their respectiveocylinders, the moment piston 3 crossed port 37 exhaust from cylinder D would take place into cylinder B behind piston13, where a partial vacuum is created and the exhaust-steam in cylinder C, which for the `moment has been undergoing compression, would then quickly move piston 24 to the end of its stroke, and exhaust would take place out through either port 29 or 29'. The back pressure that piston 2 has to overcome is net er more that the pressure necessary to force the contents of cylinder D into cylinder B. Moreover, this back pressure is exerted only at the beginning of the stroke and cannot continue beyond half-stroke.

In the drawings I illustrate certain triangular dotted-lines which merely indicate the respective points of admission and discharge. For example, air entering the perforations 35iL discharges into the port 37 and thence into the cylinder B, while air entering the perforations 17a enters the cylinder B and discharges through passage 18 in chamber 15 and passes thence through passagevli) to a reservoir.

Having thus described myinvention, what I claim, and desire to secure by Letters Patent, is-

1. The combination in a fluid-compressor, of main impelling and compressor cylinders with connected pistons moving in unison, and inlet and discharge valves therefor, and supplemental impelling and compression cylinders, connected pistons movable therein, and valves whereby the exhaust from the first impelling-cylinder is admitted to drive the piston in the second, and valves through which partially-compressed air is delivered from the second compressor-cylinder to the rst compressor-cylinder.

2. A duid-compressor consist-ing of a plurality of 'parallel impelling and compression cylinders and connected pistons in each impelling and compression cy1inder,valvechambers and valves interposed between the cylinders, whereby the exhaust from the first impelling-cylinder is admitted to the second and other valves through which air is first admitted to the second compression-cylinder, and then delivered under partial compression into the first compressor.

3. A fluid-compressor consisting of highpressure and 10W-pressure motor and compression cylinders, pistons movable therein, passages through Which the exhaust fluid from the high-pressure motor is delivered to the low-pressure motor, valves in said passages whereby the exhaust fromthe low-pressure motor is controlled, and valves through which air is first admitted to the low-pressure compressor and thence delivered under partial compression into the high-pressure compressor.

4j A duid-compressor consisting in combination of high-pressure and low-pressure impelling and compression cylinders, pistons movable therein, passages leading from the high-pressure impelling-cylinder to the low- ICO IIO

5 into said passages and adapted to be operated by the fluid-pressure in said passages, and valve mechanism through which air is first admitted to the low-pressure compressioncylinder and thence delivered into the highio pressure compression-cylinder.

5. A duid-compressor consisting in combination of a plurality of impelling and compression oylinders, pistons movable in said cylinders,connections between the impellingl5 cylinders whereby the exhaust from one is utilized as a motive power in the others, valves through which air is drawn into one of the compression-cylinders, a port entering the other compression-cylinder intermediate zo of the ends of the latter through which air under partial compression is delivered into said latter cylinder from the first cylinder.

6. The combination with high-pressu re and lowpressure compressor-cylinders, pistons movable therein, means by which said pistons are iinpelled, air-inlets in each of said cylinders through which air from the outer atmosphere is drawn in,valves in said inlets, a port entering the high-pressure compressor intermediate of the ends of the latter, connections of said port with the low-pressure compressor, Valves in said connections, the pistons in said cylinders movable oppositely in relation to each other but at different rates of speed whereby the air in the lowpressure compressor is delivered to the high-pressure cornpressor under partial compression and the latter enabled to deliver a proportionately greater quantity of air to the reservoir.

In witness whereof I have hereunto set my hand.

GEORGE W. MARSH. 

